Knowledge of the transmitters and receptors present in the vertebrate retina is essential to attempts to understand retinal function. Acetylcholine (ACh) is known to be a neurotransmitter in the vertebrate retina and much is known about the distribution and morphology of the cholinergic amacrine cells, the release of ACh, and the effects of ACh on some types of ganglion cells. Previous studies of the cholinoceptive cells have relied upon alpha-bungarotoxin. Recent studies have shown, however, that this toxin recognizes a protein which is separate from the ACh receptor. Thus, the pattern of toxin binding can no longer be considered to represent the ACh receptor distribution. The overall objectives of the proposed research are to identify and characterize the cholinoceptive neurons in the retina, elucidate their development, and to understand their relationship to the cholinergic presyaptic cells. The specific aims and the methods to achieve them follow. 1) Cells containing ACh receptors will be identified and characterized by using monoclonal antibodies directed against the ACh receptors. This technique will reveal their numbers and distribution, and their dendritic branching pattern in both the developing and adult retina. 2) The cholinoceptive ganglion cells that project to specific central retinorecipient nuclei will be characterized using a combination of immunohistochemistry and the injection of retrogradely transported markers into specific retinorecipient nuclei. 3) The size, shape and laminar pattern of cholinoceptive neurons' dendritic fields will be determined by a combination of intracellular filling of single neurons and immunohistochemistry. The dendritic patterns as revealed by the dye injection will be compared to that seen with immunohistochemistry. 4) The numbers of cells and dendritic branching pattern of the cholinoceptive cells will be compared to those of the cholinergic neurons using immunohistochemical methods. In addition, studies of the development of the cholinergic cells relative to that of the cholinoceptive cells will be studied in the same way.